The present invention relates to a process for extracting catechin polyphenols from different Potentilla species, to the extract capable of being obtained by this process and to the use of the extract obtained as active compound in the preparation of pharmaceutical, cosmetic and dietetic compositions.
Many plants are known to contain polyphenols containing oxygen heterocycles, termed "flavonoids" in the broad sense, such as catechins (proanthocyanidins), flavanones, flavonols, anthocyanins and the like. The present invention relates to a process for extracting, from Potentilla, catechin polyphenols or 3-flavanol derivatives, among which epicatechol, catechol and oligomers of these compounds, especially procyanidins, may be mentioned.
According to the invention, the extraction of these catechin polyphenols is carried out from various Potentilla species. Among these species, there may be mentioned tormentil (Potentilla tormentilla Neck, also known as Tormentilla erecta L., Tormentilla reptans L., Tormentilla officinalis Curt, Potentilla tetrapetala Hall, Fragaria tormentilla Granz), silverweed (Potentilla anserina L. or Argentina Vulgaris Lam.) and cinquefoil or creeping cinquefoil (Potentilla reptans L.).
The various Potentilla species, and especially tormentil, have already been used in traditional medicine. They were administered in various forms: as powder, decoction or maceration; they were used to treat acute or chronic inflammatory disorders of the gastrointestinal mucosae, or as antiseptics in the form of mouthwashes or gargles, or alternatively to treat pharyngitis.
Moreover, scientific studies have demonstrated the presence of catechin polyphenols in various Potentilla species, especially Potentilla erecta L. In this connection, there may be mentioned C.A. 63, 9742 h, which mentions the presence of tannins in Potentilla erecta; C.A. T 63, 10314 e, which mentions the presence of myricetin and of leucodelphinidin in Potentilla erecta and the presence of ellagic acid in practically all Potentilla species; and C.A. 71, 10266 w, which mentions the presence of (+)-catechol in Potentilla fruticosa and Potentilla anserina and the presence of (-)-epicatechol in Potentilla anserina.
The properties of the potentillas used in traditional medicine are probably due to the presence of catechin polyphenols. Moreover, it is known to use catechin polyphenols, for example extracted from pine bark, in therapy for improving venous wall tonicity, as a vitamin C cofactor or for improving blood circulation. These polyphenols have, in a known manner, free radical-scavenging properties, which enables them to be used in dietetics as a food supplement for preventing atherosclerosis and in cosmetology for combatting cell ageing or the appearance of skin cancers. Furthermore, catechin polyphenols may serve as photoprotective agents on account of their good absorption of ultraviolet light.
Several processes for extracting catechin polyphenols from various plants, such as grape pips and pine bark, have been described in U.S. Pat. No. 4,698,360, EP-A-348, 781, EP-A-283, 349, FR-A-1,427,100, FR-A-2,092,743, FR-A-2,643,073 and FR-A-2,372,823. According to these documents, the plant is treated with water (especially hot water) or a mixture of water and a ketone in variable proportions, and the extract obtained is then treated using a concentrated salt solution so as to precipitate the high molecular weight tannins which are of no therapeutic interest; however, the use of a saline solution is detrimental to the environment and builds an additional cost into the finished product. Carrying out the purification by ultrafiltration through suitable membranes has also been proposed. All of these processes, however, do not permit a catechin polyphenol-rich extract to be obtained from potentillas, especially one which is rich in catechin oligomers and which possesses a sufficiently high degree of purity to be able to be used in man.